Particle beam irradiation apparatus and particle beam irradiation method

ABSTRACT

To ensure irradiation accuracy and safety, even when an irradiation device employing a different irradiation method is used, disclosed is herein a charged particle beam irradiation apparatus that irradiates an irradiation target with charged particle beams includes: 
     a charged particle beam generator for generating the charged particle beams; a passive scattering irradiation device and a scanning irradiation device, both for irradiating the irradiation target with the charged particle beams; a beam transport system for transporting the charged particles beam extracted from the charged particle beam generator, to selected one of the two irradiation devices; and a central controller that modifies operating parameters on the charged particle beam generator, according to the irradiation method adopted for the selected irradiation device.

BACKGROUND OF THE INVENTION

The present invention relates to the particle beam irradiation apparatusand particle beam irradiation method used for irradiating affectedregions with charged particle beams such as proton or carbon ion beamsin order to provide medical care.

Among known medical treatment methods is one in which the affectedregions of patients who are suffering from diseases such as cancer areirradiated with proton, carbon ion, or other charged particle beams. Thelarge-scale charged particle beam irradiation apparatus used in thistreatment method has a charged particle beam generator, a beam transportsystem, and a plurality of irradiation devices. A charged particle beamthat has been accelerated by the charged particle beam generator reachesselected one of the plural irradiation devices through the beamtransport system, and then the beam is emitted from the nozzle of theirradiation device to the affected region of the patient lying on atreatment couch. In general, for such a charged particle beamirradiation apparatus with a plurality of irradiation devices, theseirradiation devices are connected to one charged particle beam generatorand beams can be transported to a desired irradiation device by changingbeam transport system data settings (refer to JP-A-11-501232, forexample).

Passive scattering and pencil beam scanning are known as the irradiationmethods used for irradiation apparatus. Passive scattering is anirradiation method in which beams are spread by a scattering device andthen shaped to fit to the particular shape of the affected region, andpencil beam scanning is an irradiation method in which the inside of theaffected region is scanned with narrow beams (refer to Japanese PatentNo. 2833602, for example).

SUMMARY OF THE INVENTION

In general, the scanning method has the feature that an absorbed dosedistribution more matching the shape of the affected region can beobtained than with the passive scattering method. Accordingly, practicaluse of the scanning method in medical care is increasing in recentyears. Conventional charged particle beam irradiation apparatus with aplurality of irradiation devices has usually employed irradiationdevices based on passive scattering. However, since practical use of thescanning method is increasing in recent years as mentioned above,charged particle beam irradiation apparatus with the plurality ofirradiation devices which include irradiation devices of differentirradiation schemes such as scanning and passive scattering is likely tobe placed in practical use in the future.

The present inventors studied the scanning method and the passivescattering method to find out the following problems. That is to say, inthe scanning method that requires changing an irradiation position,energy, and other irradiation parameters in order while changingapparatus component data settings according to the particular dosedistribution, if the beam intensity of the beam transported to anirradiation device is too great, this could deteriorate irradiationaccuracy since it may become impossible to follow up changed apparatuscomponent data settings. Also, since narrow beams are used,instantaneous peak dose rates tend to increase, so it is desirable thatpartly in terms of safety during medical treatment irradiation, the beamintensity be moderately lowered. In addition, since the scanning methoduses narrow beams, there is a need to suppress the beam size of thebeams transported.

In the passive scattering method, however, since beams are spread byscattering devices and then directed to a target object, there arelittle problems with the irradiation accuracy and safety discussedabove. To shorten the treatment time required, it is desirable that thebeam intensity be moderately increased for higher dose rates. Therefore,beams whose irradiation parameters differ according to irradiationdevice should be transported to implement the medical treatmentirradiation that is highly efficient and satisfies the irradiationaccuracy and safety required of, for example, the above-mentionedcharged particle beam irradiation apparatus having irradiation devicesbased on both scanning and passive scattering. In other words, datasettings on the charged particle beam generator that generates chargedparticle beams are desirably modified according to the kind ofirradiation device (i.e., the irradiation method) used for the treatmentirradiation.

For the conventional charged particle beam irradiation apparatus havinga plurality of irradiation devices, however, equivalent parameters suchas beam intensity and beam size have always been used for the chargedparticle beam generator to emit beams to whichever irradiation device.For this reason, even when the conventional charged particle beamirradiation apparatus was provided with irradiation devices of differentirradiation schemes such as scanning and passive scattering, it has beenimpossible to supply to the selected irradiation device the beamsmatching its irradiation scheme. Therefore, there has been room forimprovement in terms of irradiation accuracy and safety.

The present invention was made in view of the above problems associatedwith the conventional technology, and an object of the invention is toprovide: a charged particle beam irradiation apparatus capable ofensuring irradiation accuracy and safety, even if provided with theirradiation devices that use different irradiation methods; and aparticle beam irradiation method used for the apparatus.

In order to achieve the above object, a charged particle beamirradiation apparatus of the present invention, designed to extractcharged particle beams and emit the beams to an irradiation target,includes: a charged particle beam generator for generating the chargedparticle beams; a plurality of irradiation devices each for irradiatingthe irradiation target with the charged particle beams, wherein at leasta part of the irradiation device group applies a different irradiationmethod; a beam transport system for transporting the charged particlebeams extracted from the charged particle beam generator, to selectedone of the irradiation devices; and a controller that modifies operatingparameters of the charged particle beam generator according to theirradiation method adopted for the selected irradiation device.

In the present invention, charged particle beams suitable for theirradiation method adopted for the selected irradiation device can betransported thereto in order to modify operating parameters of thecharged particle beam generator according to the above irradiationmethod. Irradiation accuracy and safety can thus be ensured.

Preferably, the irradiation apparatus further has a detector fordetecting a beam state of the charged particle beams extracted from thecharged particle beam generator, and a judging device for judgingwhether the beam state that has been detected is normal, and modifiesjudgment parameters of the judging device according to the irradiationmethod adopted for the selected irradiation device. This makes itpossible to accurately judge whether the charged particle beamstransported to the selected irradiation device are suitable for theirradiation method adopted therefor.

According to the present invention, irradiation accuracy and safety canthus be ensured, even if the irradiation apparatus has the irradiationdevices that use different irradiation methods.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent fromthe following description of embodiments with reference to theaccompanying drawings in which:

FIG. 1 is a total configuration diagram of a charged particle beamirradiation apparatus which is a preferred embodiment of the presentinvention;

FIG. 2 is a flowchart that shows process steps up to medical treatmentirradiation;

FIG. 3 is a diagram that shows examples of the operating parameter datalists selected by a central controller and transmitted therefrom to anaccelerator controller in process step 38 or 40 of FIG. 2;

FIG. 4 is a diagram in which, in the charged particle beam irradiationapparatus of the present embodiment, features of the operating parameterdata list transmitted from the central controller to the acceleratorcontroller are represented so that differences between a passivescattering irradiation method and a scanning irradiation method canbetter be understood;

FIG. 5 is a diagram showing the relationship between the beam energydata and to-be-extracted beam intensity data specified in an operatingparameter data list for passive scattering and in an operating parameterdata list for scanning; and

FIG. 6 is a total configuration diagram of a charged particle beamirradiation apparatus which is another embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described in detailhereunder using the accompanying drawings.

First Embodiment

First, a charged particle beam irradiation apparatus that is a preferredembodiment of the present invention is described below using FIG. 1.

A charged particle beam irradiation apparatus 100 of the presentembodiment has a charged particle beam generator 1, a beam transportsystem 2 connected to an output end of the charged particle beamgenerator 1, and two irradiation devices, 3 s and 3 p, that operate asirradiation field forming devices. More specifically, the chargedparticle beam irradiation apparatus 100 of the present embodiment is aproton beam irradiation apparatus.

The charged particle beam generator 1 has an ion source (not shown), apre-accelerator (e.g., a linear accelerator) 4, and a synchrotron 5 thatis a main accelerator. In the synchrotron 5, a high-frequency beamextraction device 6 formed with one pair of electrodes, and ahigh-frequency beam accelerating cavity 7 are installed on a circularrevolution orbit of ion beams. A first high-frequency power supply (notshown) is connected between the electrodes of the high-frequency beamextraction device 6, and an independent second high-frequency powersupply (not shown) is provided for the high-frequency beam acceleratingcavity 7. An ion beam, e.g., proton (or carbon ion) beam that has beengenerated by the ion source is accelerated by the pre-accelerator 4.After being extracted from the pre-accelerator 4, the ion beam (chargedparticle beam) enters the synchrotron 5. The ion beam, a chargedparticle beam, is accelerated by the energy applied according toparticular strength of the electromagnetic field generated in thehigh-frequency beam accelerating cavity 7 by application ofhigh-frequency electric power from the second high-frequency powersupply. The ion beam that revolves inside the synchrotron 5 isaccelerated to previously set energy (e.g., 100 to 200 MeV) and thenextracted from the synchrotron 5. That is to say, high-frequencyelectric power from the first high-frequency power supply is applied tothe revolving ion beam via the high-frequency beam extraction device 6.Accordingly, the ion beam revolving within safety limits moves outtherefrom and is extracted through an extraction deflector 8. When theion beam is extracted, an electric current conducted into quadrupoleelectromagnets (not shown) of the synchrotron 5 and into bending magnets10 is maintained at an electric current data setting and the safetylimits are also kept almost constant. The extraction of the ion beamfrom the synchrotron 5 is stopped by a stop of high-frequency electricpower application to the high-frequency beam extraction device 6. Also,the first high-frequency power supply connected to the high-frequencybeam extraction device 6 is controlled in accordance with the datasettings prestored in association with the beam energy and beamintensity, and thus a beam of desired beam intensity is extracted fromthe synchrotron 5.

The two irradiation devices, 3 s and 3 p, are arranged in independenttreatment rooms, and the ion beam from the charged particle beamgenerator 1 is transported to a selected treatment room by the beamtransport system 2. The irradiation device 3 p, one of the twoirradiation devices, is a passive scattering irradiation device, and theirradiation device 3 s that is the other of the two irradiation devicesis a scanning irradiation device. Hereinafter, the treatment rooms wherethe irradiation devices 3 p, 3 s are arranged are called “scatteringtreatment room 11 p” and “scanning treatment room 11 s”, respectively.Although not shown, a treatment bed for immobilizing a patient at anappropriate position, an X-ray fluoroscopic apparatus for obtainingfluoroscopic images of the patient, and other equipment are arranged inthe treatment rooms 11 p, 11 s.

The synchrotron 5 also has a beam scraping device 15 on the orbit of theion beam revolving in the synchrotron. The beam scraping device 15 has ascraper (not shown) that is a metallic block whose distance from thecircular revolution orbit of the beam can be adjusted. Moving thescraper closer to the circular revolution orbit of the beam chips off apart of the beam for a reduced beam size. The synchrotron 5 further hasa frequency monitor (detector) 16 for measuring a circular revolutionfrequency of the beam, a circular revolution orbit position monitor(detector) 17 for measuring a circular revolution orbit position, and amagnetic field monitor (not shown) for measuring magnetic field strengthof the bending magnets of the synchrotron. The measurement resultsobtained from the monitors 16 and 17 after the ion beam has beenaccelerated are output to an accelerator controller 24 described laterherein, and it is judged whether deviations between output measurementresults and the prestored data settings mentioned above stay within anallowable range. In this way, the accelerator controller 24 judgeswhether the ion beam revolving in the synchrotron 5 has a desired beamenergy level. If the output measurement results contain onesoverstepping the allowable range, the accelerator controller 24 outputsan error signal to a central controller 23 described later herein. Thus,the central controller 23 controls the charged particle beam generator 1via the accelerator controller 24 and directly decelerates the beamwithout extracting the beam. If all output measurement results arejudged to stay within the allowable range, high-frequency electric poweris applied to the high-frequency beam extraction device 6, whereby theextraction of the ion beam from the synchrotron 5 is started.

The ion beam that has been extracted from the synchrotron 5 istransported to the output end thereof by the beam transport system 2.The beam transport system 2 has a plurality of bending magnets (notshown) and quadrupole magnets (not shown), and beam paths 2 p and 2 scommunicated with the passive scattering irradiation device 3 p andscanning irradiation device 3 s arranged in the two treatment rooms 11 pand 11 s, respectively. The quadrupole magnets and bending magnetsconstituting the beam transport system 2 are set so that in accordancewith a command from a transport system controller 25 described laterherein, the ion beam that has been extracted from the synchrotron 5 istransported to either the passive scattering irradiation device 3 p orthe scanning irradiation device 3 s, whichever is selected. The ionbeam, after being introduced into the beam transport system 2, istransported to the passive scattering irradiation device 3 p through thebeam path 2 p or to the scanning irradiation device 3 s through the beampath 2 s.

The beam transport system 2 also includes a beam profile monitor(detector) 20 for measuring a position and width of the ion beam to betransported, and a beam intensity monitor (detector) 21 that measuresintensity of an electric current of the beam to be transported. Thetransport system controller 25 acquires an output from the profilemonitor 20 and an output from the beam intensity monitor 21, at fixedsampling time intervals. Next, the transport system controller 25judges, by checking against the prestored data settings, whether thegravitational position and beam size of the beam, calculated from theoutput of the profile monitor 20, and the output of the beam intensitymonitor 21 depart from the allowable range. If either of the outputs isjudged to be outside the allowable range, an error signal is output tothe central controller 23. Beam extraction is thus stopped.

Although this is not shown in the figure, the passive scatteringirradiation device 3 p provided in passive scattering treatment room 11p includes various constituent elements. Examples include: a scatteringdevice for scattering a beam, a flatness monitor for measuring anas-scattered distribution of the beam, a dose monitor for measuring abeam energy dose, an energy modulation device for adjusting adepth-direction dose distribution, and a collimator for forming the beaminto a necessary shape.

The ion beam that has been supplied via beam transport system 2 p isspread in a direction vertical to a traveling direction of the beam, bythe scattering device, and then adjusted to an appropriate energydistribution by the energy modulation device. Next, this beam is shapedby the collimator to fit to the shape of an affected region to beirradiated with the beam, and the patient who is the irradiation targetis irradiated. When an integrated beam dose reaches a previously plannedand set value, an ending signal of the irradiation is transmitted to thecentral controller 23. This completes the irradiation.

Although this is not shown in the figure, the scanning irradiationdevice 3 s has scanning magnets for scanning a beam, a beam positionmonitor for measuring a position of the scanning beam, a dose monitorfor estimating the irradiation dose, and other elements. An irradiationposition of the ion beam that has been supplied via beam transportsystem 2 s is adjusted by the scanning magnets, and then the patient whois the irradiation target is irradiated with the beam. The irradiationposition and energy of the ion beam are previously planned and set as aparameter list associated with the integrated beam dose. As theintegrated beam dose increases, the irradiation position and the energyare changed, and when the integrated beam dose reaches the previouslyplanned and set value, an ending signal of the irradiation istransmitted to the central controller 23. This completes theirradiation.

The charged particle beam irradiation apparatus 100 of the presentembodiment further has a control system 101. The control system 101includes: a treatment managing system 22; a central controller (secondcontroller) 23; an accelerator controller (judging device) 24 forcontrolling the charged particle beam generator 1; a transport systemcontroller (judging device) 25 for controlling the beam transport system2; a passive scattering irradiation controller 26 p for controlling thepassive scattering irradiation device 3 p; and a scanning irradiationcontroller 26 s for controlling the scanning irradiation device 3 s.

The treatment managing system 22 has a database function to manageirradiation parameter data and irradiation schedules. Stored irradiationparameter data within the treatment managing system 22 differs accordingto the particular irradiation method. For the passive scattering method,the data consists of, for example, the energy, irradiation direction,irradiation range, irradiation dose, and other factors of the beam. Forthe scanning method, the energy, beam size, irradiation position, andother factors of the beam constitute list data associated with theintegrated dose. The treatment managing system 22 is connected to animage acquisition system (not shown) that acquires the images used forCT and other diagnostic purposes, and to a patient informationmanagement database (not shown) that manages data on patients.

Process steps for medical treatment irradiation with the thus configuredcharged particle beam irradiation apparatus 100 of the presentembodiment are described below using FIG. 2. FIG. 2 is a flowchart thatrepresents process steps up to medical treatment irradiation.

Under user operations from the treatment room (step 31), the centralcontroller 23 first reads in the irradiation parameter data required fornext irradiation, from the treatment managing system 22 (step 32). Theirradiation parameter data has been previously created by a treatmentplanning system (not shown) and registered in the treatment managingsystem 22. In step 32, the central controller 23 reads in irradiationparameter data for 3 p if the user operations in step 31 are performedfrom passive scattering treatment room 11 p, or reads in irradiationparameter data for 3 s if the user operations are performed fromscanning treatment room 11 s. In this manner, it is discriminatedwhether the irradiation parameter data is for the passive scatteringirradiation device 3 p or for the scanning irradiation device 3 s.Instead of this method, the irradiation parameter data itself may beendowed with information concerning the irradiation device (or theirradiation method), and the central controller 23 may be caused toconduct a discrimination based on the information.

In step 33, 34, or 35, it is judged whether discrepancies exist betweenthe irradiation device information contained in the irradiationparameter data, and an operating location of the user. Processing isterminated in step 36 if discrepancies exist (e.g., if the irradiationparameter data for the scanning irradiation device 3 s is called up fromthe passive scattering treatment room 11 p, or vice verse).

Next, on the basis of the irradiation parameter data that it has readin, the central controller 23 selects operating parameter data on thecharged particle beam generator 1 (synchrotron 5) and other constituentdevices, from a pre-registered data list. Data that has thus beenselected is transmitted to each controller (accelerator controller 24,transport system controller 25, and irradiation controller 26 s, 26 p)in step 37, 38, 39, or 40. For example, if attention is focused on theaccelerator controller 24, the data list transmitted in the presentembodiment is for scanning use or for passive scattering use. This datalist includes the operation pattern data (magnet pattern IDs and others)of the synchrotron 5 that is associated with various energy levels, andinformation such as a high-frequency electric power output to be appliedto the high-frequency beam extraction device 6 (see the description ofFIG. 3, given later herein). The central controller 23 uses either thepassive scattering data list if the irradiation parameter data is forpassive scattering use, or the scanning data list if the irradiationparameter data is for scanning use, and acquires magnet pattern IDs andother operating parameter data from the beam energy data specified inthe irradiation parameter data. Acquired operating parameter data istransmitted to the accelerator controller 24.

Each controller sets up each device on the basis of the operatingparameter data transmitted from the central controller 23. Afterconfirming completion of the setup, each controller transmits anirradiation ready signal to the central controller 23 (steps 41, 42).Thus, the central controller 23 makes irradiation startup operationsvalid and outputs a ready signal to computer terminals in each treatmentroom 11 s, 11 p. Subsequently, when an irradiation startup signal isoutput by user operations, operation of the synchrotron 5 is started andtreatment irradiation based on data settings is initiated. If the setupof each device by each controller has not come to a normal end, anirradiation operational setup error occurs and processing is terminated(step 43).

The accelerator controller 24 controls the first highfrequency powersupply on the basis of the data of highfrequency electric power (one ofthe operating parameter data) transmitted from the central controller23. Thus the first highfrequency power supply outputs less electricpower for irradiation by the scanning irradiation device 3 s than forirradiation by the passive scattering irradiation device 3 p. Becausethe less electric power is applied into the high-frequency beamextraction electric device 6, the smaller intensity ion beam extractedfrom the synchrotron 5 is supplied to the scanning irradiation device 3s. In addition, in the case that the scanning irradiation device 3 s isselected, the accelerator controller 24 controls the position of thescraper 15 based on the data tranmitted from the central controller 23so as to reduce the beam size.

Examples of the operating parameter data lists selected by the centralcontroller 23 and transmitted therefrom to the accelerator controller 24in process step 38 or 40 of FIG. 2 are shown in FIG. 3. In thesynchrotron 5 of the present embodiment, a spread of the ion beamrevolving as mentioned above is increased by the application ofhigh-frequency electric power to the high-frequency beam extractiondevice 6 and then extracted from the extraction deflector 8. It ispossible, by adopting an extraction method that uses a high-frequencyelectric field in this way, to extract beams of a stable size andposition, and to easily adjust beam intensity. As the high-frequencyelectric power increases, the ion beam spreads more rapidly and a rateof its injection into the beam deflector 8 also increases. This, inturn, increases the beam intensity of the ion beam extracted. Inaddition, since an ion beam of the lower beam energy spreads by thehigh-frequency electric field more rapidly, the beam intensity of theion beam extracted by the same high-frequency electric power increaseswith a decrease in beam energy. As shown in FIG. 3, in the data list forpassive scattering, data is set so that the high-frequency electricpower decreases with a decrease in beam energy and so that almostconstant beam intensity is extracted, regardless of the energy. Inassociation with this, an upper limit of the beam intensity is alsofixed at a constant value. In the data list for scanning, data is set sothat the high-frequency electric power decreases below of passivescattering and so that the beam intensity of the ion beam extracted isdiminished with decreases in beam energy. In association with this, thebeam intensity upper limit is set to totally decrease in comparison withthat of passive scattering and to be lowered with decreases in beamenergy.

Also, the scraper position shown in FIG. 3 is distanced from thecircular revolution orbit of the beam on the scraper, as mentionedearlier. Longer distance from the orbit means that the amount of beamchipped is smaller. In the present embodiment, the above distance forpassive scattering is set to such a value that does not limit the beamsize, and the above distance for scanning is set to such a value thatreduces the beam size by chipping the beam. In this way, little beamsare chipped for the passive scattering irradiation method that requiresa large number of beams, and the beam size is reduced for the scanningirradiation method that requires narrow beams.

In addition, a circular revolution frequency range of the ion beam isset to a large value for passive scattering, and a small value forscanning. In this way, a wide allowable energy range is employed for thepassive scattering method that does not deteriorate irradiation accuracytoo significantly with respect to a change in beam energy, and a narrowallowable energy range is employed for the scanning method.

Although this is not shown in FIG. 3, in the operating parameter datalist transmitted from the central controller 23 to the transport systemcontroller 25, an allowable beam position setting range for irradiationin the passive scattering treatment room 11 p is wider than forirradiation in the scanning treatment room 11 s.

FIG. 4 is a diagram in which features of the operating parameter datalist transmitted to the central controller 24 and accelerator controller25 in the present embodiment described above are represented so thatdifferences between the passive scattering irradiation method and thescanning irradiation method can better be understood. As shown in FIG.4, the set beam intensity value and set beam size value transmitted tothe accelerator controller 24 and used for irradiation in the passivescattering treatment room lip are greater than for irradiation in thescanning treatment room 11 s. The allowable energy range data andallowable beam position range data transmitted to the acceleratorcontroller 24 and the transport system controller 25, respectively, forirradiation in the passive scattering treatment room 11 p are alsogreater than for irradiation in the scanning treatment room 11 s.

The charged particle beam irradiation apparatus 100 of the presentembodiment offers the following advantageous effects. That is, in thepassive scattering irradiation method, irradiation accuracy does notgreatly depend on the intensity of the beam current from the chargedparticle beam generator 1. This is because states of the beams for theirradiation of the patient (i.e., the spread and energy distribution ofthe beams) are typically determined by specifications of the scatteringdevice, energy modulation device, collimator, and other devices arrangedfor the irradiation apparatus. In addition, changes in dose distributionare small with respect to changes in beam energy. For these reasons,increases in the beam intensity or slight variations in beam energy donot deteriorate irradiation accuracy very much.

In the scanning irradiation method, however, irradiation positions,energy, and other irradiation parameters are sequentially changedaccording to the integrated dose, so if the beam intensity of the beamtransported to the irradiation device is too great, devices becomeunable to follow up too quick parameter change and irradiation accuracywould be deteriorated. Also, since narrow beams are used, instantaneouspeak dose rates tend to increase, so it is desirable that partly interms of safety during medical treatment irradiation, the beam intensitybe moderately lowered. In addition, since the scanning method usesnarrow beams, there is a need to suppress the beam size of the beamstransported.

For these reasons, in the charged particle beam irradiation apparatus100 having both passive scattering and scanning types of irradiationdevices 3 s and 3 p as in the present embodiment, beams whoseirradiation parameters differ according to a particular irradiationmethod need to be supplied to associated irradiation device 3 s or 3 pto conduct the treatment irradiation that satisfies the irradiationaccuracy and safety required.

In the charged particle beam irradiation apparatus 100 of the presentembodiment, therefore, as described above, charged particle beamssuitable for the irradiation method adopted for a selected irradiationdevice can be supplied to the irradiation device 3 s or 3 p in order tomodify the operating parameters of the charged particle beam generator1. It is thus possible to ensure irradiation accuracy and safety. Sincethe circular revolution frequency range of the ion beam is set to alarge value for passive scattering, and a small value for scanning, itis also possible to enhance irradiation efficiency by employing a wideallowable energy range for the passive scattering method that does notdeteriorate irradiation accuracy too significantly with respect to achange in beam energy. In addition, it is possible to monitor fornecessary irradiation accuracy by employing a narrow allowable energyrange for the scanning method. For these reasons, irradiation accuracyand safety can be reliably secured.

Furthermore, in the present embodiment, the data list for scanning isset so that as described above, beam intensity is lowered with decreasesin beam energy. The relationship between the beam energy data andto-be-extracted beam intensity data specified in the operating parameterdata list for passive scattering and in the operating parameter datalist for scanning is shown in FIG. 5. Since, as can be seen from thisfigure, the data list for scanning is set so that beam intensity islowered with decreases in beam energy, beam intensity can beappropriately set for and monitored during the scanning irradiation thatrequires controlling the beam intensity to a small value for usingnarrow beams. This allows irradiation accuracy and safety to be securedmore reliably.

While it has been described heretofore that an upper-limit value is notprovided for the high-frequency beam extraction electric power appliedby the high-frequency beam extraction device 6, an upper limit ofhigh-frequency beam extraction electric power for irradiation by thescanning irradiation device 3 s may be set to a value smaller than anupper limit of high-frequency beam extraction electric power forirradiation by the passive scattering irradiation device 3 p. Thisallows reliable limitation of the extraction current supplied in thescanning method, and hence, further improvement of safety.

It has also been described heretofore that beam intensity is adjustedaccording to a particular high-frequency beam extraction electric powerlevel and that the beam size is adjusted by the beam scraping device 15.When the beam is chipped by inserting a scraper, the beam is narroweddown and at the same time, the beam current inside the synchrotron 5decreases to diminish the beam intensity of the beam extracted. Thisproperty may be utilized to adjust the beam intensity and the beam sizeat the same time according to the amount of scraper insertion by thebeam scraping device 15.

In addition, although only setup parameters equivalent to one kind ofbeam intensity for each beam energy level are shown in FIG. 3,specification of irradiation parameter data or selection of beamintensity by an operator may be conducted after a plurality of beamintensity values have been provided. In that case, the high-frequencybeam extraction electric power level may be changed according to thebeam intensity selected, and at the same time, changes may also be madeto an upper-limit value of the beam intensity, a position of thescraper, and other parameters. Thus, greater flexibility in response toa request for more advanced treatment irradiation can be obtained and atthe same time, irradiation accuracy and safety can be improved.

Furthermore, while an example of providing two kinds of data lists, onefor scanning irradiation and one for passive scattering irradiation, isshown in the present embodiment, it may also be possible to provide alarger number of kinds of data lists, including those intended forirradiation devices of different irradiation field sizes, or to provideindependent data lists for each treatment room. Thus, even in a systemthat requires beams whose irradiation parameters differ, it is possibleto realize each of the parameters automatically and appropriately and toimprove accuracy and safety.

In the case that the size of the ion beam extracted from the synchrotron5 is adequately narrow for the scanning irradiation, it may also bepossible to apply the same setting of the beam size for both scanningirradiation and passive scattering irradiation. In this case, it is alsopossible to control the beam intensity in accordance with the selectedirradiation device. Specifically for present embodiment, as describedabove, it can be realized by setting the first highfrequency powersupply so that it output less electric power for irradiation by thescanning irradiation device 3 s than for irradiation by the passivescattering irradiation device 3 p.

Second Embodiment

A charged particle beam irradiation apparatus that is another embodimentof the present invention is described below using FIG. 6. Chargedparticle beam irradiation apparatus 100A of the present embodiment isadapted to include: a charged particle beam generator 1A with acyclotron 5A, instead of the charged particle beam generator 1 with asynchrotron 5 in the charged particle beam irradiation apparatus 100;and a control system 101A with an added second passive scatteringtreatment room, an operational state monitoring device (judging device)45, and an added second passive scattering irradiation controller forthe added treatment room, instead of the control system 101 in theirradiation apparatus 100.

The charged particle beam irradiation apparatus 100A has the chargedparticle beam. generator 1A equipped with the cyclotron 5A by whichincident beams from an ion source (not shown) are accelerated to desiredenergy, a beam transport system 2A connected to an output end of thecharged particle beam generator 1A, and three irradiation treatmentrooms. The three irradiation treatment rooms are a scanning treatmentroom 11 s with an installed scanning irradiation device 3 s, and passivescattering treatment rooms 11 p 1 and 11 p 2 with installed passivescattering irradiation devices 3 p 1 and 3 p 2, respectively. Thecyclotron 5A that generates beams of fixed energy as charged particlebeams essentially of a continuous current, has an energy adjustingsystem (energy selection system) 46 for degrading and selecting thebeams. The energy adjusting system 46, although described hereinafter asbeing included in the charged particle beam generator 1A, may beincluded in a beam transport system 2.

The beams of fixed energy that have been extracted from the cyclotron 5Athrough a beam deflector 47 have the energy absorbed by a degrader 48,thus providing desired energy necessary for irradiation. The beams thathave been significantly scattered by the degrader 48 are cut by anemittance aperture 49, then bent by an energy analyzing magnet 50, andbeams whose energy has deviated from the desired energy are cut by anenergy aperture device 51. The degrader 48, the emittance aperture 49,the energy analyzing magnet 50, and the energy aperture device 51constitute the energy adjusting system 46 that selects beam energy andadjusts a beam size. In the energy aperture device 51, plural kinds ofapertures with different aperture sizes are selectively provided andthese apertures are each selected by an accelerator controller 24,whereby the beam size is controlled. The energy analyzing magnet 50 hasan energy-analyzing magnetic field monitor (not shown), by which theenergy of the beams is monitored.

Beam transport system 2A has beam paths 2 p 1, 2 p 2, and 2 s, which arecommunicated with the passive scattering irradiation devices 3 p 1, 3 p2 and scanning irradiation device 3 s arranged in the three treatmentrooms, 11 p 1, 11 p 2, and 11 s, respectively. In the beam transportsystem 2A, similarly to the first embodiment, a beam profile monitor 20and a beam intensity monitor 21 are arranged to monitor a state of thebeam.

In addition to the control system components in the first embodiment,the control system 101A has an operational state monitoring device 45.The operational state monitoring device 45 reads an output of anenergy-analyzing magnetic field monitor (not shown) provided at theenergy analyzing magnet 50, an output of the profile monitor 20 in thebeam transport system 2A, and an output of the beam intensity monitor21, at fixed sampling time intervals. Next, the operational statemonitoring device 45 judges, by checking against prestored datasettings, whether the gravitational position and beam size of the beam,calculated from the magnetic field monitor output and the output of theprofile monitor 20, deviate from an allowable range. If either of theoutputs is judged to be outside the allowable range, an error signal isoutput to a central controller 23, thus causing the synchrotron 5A tostop supplying beams.

Apparatus components other than those described above, and irradiationprocess steps are basically the same as in the first embodiment. In thepresent second embodiment, however, the charged particle beam generatorlA includes the synchrotron 5A and the energy adjusting system 46, sothe kinds of operating parameter data items transmitted from the centralcontroller 23 to the accelerator controller 24 differ as describedbelow.

On the basis of the irradiation parameter data that it has read in, thecentral controller 23, as with that of the first embodiment, selectsoperating parameter data on the charged particle beam generator 1A(cyclotron 5A) and other constituent devices, from a pre-registered datalist. Data that has thus been selected is transmitted to eachcontroller, that is, an accelerator controller 24, transport systemcontroller 25, and irradiation controller 26 s, 26 p 1, 26 p 2. Either adata list for scanning, or a data list for passive scattering istransmitted to the accelerator controller 24. Each such data listincludes information such as: ion source electric-current data settingsassociated with various energy levels, operational data on the energyanalyzing magnet 50, and the kinds of apertures in the energy aperturedevice 51.

Although this is not shown in FIG. 6, in the present embodiment,electric-current data settings for the ion source are relatively highfor passive scattering, and relatively small for scanning. Also, thekinds of apertures in the energy aperture device 51 are set so that forpassive scattering, each aperture takes a large aperture size, and sothat for scanning, beams are chipped and dimensionally narrowed down foreach aperture.

Thus, an allowable energy range for passive scattering is spread andthat of scanning is narrowed. Also, in the operating parameter data listtransmitted from the central controller 23 to the transport systemcontroller 25, an allowable beam position setting range for passivescattering is wider than that of scanning.

As can be seen from the above, similarly to the first embodiment, asshown in FIG. 4, the set beam intensity value and set beam size valuetransmitted to the accelerator controller 24 and used for irradiation inthe passive scattering treatment room 11 p 1, 11 p 2, are greater thanfor irradiation in the scanning treatment room 11 s. The allowableenergy range data and allowable beam position range data transmitted tothe accelerator controller 24 and the transport system controller 25,respectively, for irradiation in the passive scattering treatment room11 p 1, 11 p 2, are also greater than for irradiation in the scanningtreatment room 11 s.

Irradiation accuracy and safety, therefore, can also be ensured in thepresent embodiment. Additionally, according to the present embodiment,energy, beam intensity, beam positions, width, and other parametersrepresenting an operational state are monitored by the operational statemonitoring device 45 provided independently of the acceleratorcontroller 24 and the transport system controller 25. This allows adesired operational state to be monitored for, even in case of a singlefailure such as a malfunction in the accelerator controller 24, andthus, safety to be improved further.

It has also been described heretofore that beam intensity is adjusted bysetting the ion source electric-current and that the beam size isadjusted by selecting an aperture device 51. When beam size is adjustedby the aperture device 51, the beam is narrowed down and at the sametime, the beam intensity pass through the aperture device 51 isdecreased. This property may be utilized to adjust the beam intensityand the beam size at the same time according to the selecting anaperture device 51. In the case that the size of the ion beam extractedfrom the cyclotron 5A is adequately narrow for the scanning irradiation,it may also be possible to apply the same setting of the beam size forboth scanning irradiation and passive scattering irradiation. In thiscase, it is also possible to control the beam intensity in accordancewith the selected irradiation device. Specifically for presentembodiment, it can be realized by setting the ion sourceelectric-current data so that it output less ion beam for irradiation bythe scanning irradiation device 11 s than for irradiation by the passivescattering irradiation device 11 p 1 or 11 p 2.

While operating parameters on high-frequency beam extraction electricpower, on a beam current upper limit, on a scraper position, onfrequency ranges, on ion source electric-current data settings, and onthe kinds of apertures, are designed so as to be modified in the twoembodiments described above, the present invention is not limited to/bythis modification form and other operating parameters may also bemodified. Irradiation accuracy and safety can likewise be improved byassigning appropriate data to other parameters as well, irrespective ofwhether scanning or passive scattering is employed.

While the invention has been described in its preferred embodiments, itis to be understood that the words which have been used are words ofdescription rather than limitation and that changes within the purviewof the appended claims may be made without departing from the true scopeand spirit of the invention in its broader aspects.

1. A charged particle beam irradiation apparatus that irradiates an irradiation target with a charged particle beam, said apparatus comprising: a charged particle beam generator for generating the charged particle beam; a plurality of irradiation devices each for irradiating the irradiation target with the charged particle beam, wherein at least a part of said irradiation device group applies a different irradiation method; a beam transport system for transporting the charged particle beam extracted from said charged particle beam generator, to selected one of said irradiation devices; and a controller that modifies operating parameters of said charged particle beam generator according to the irradiation method adopted for said selected irradiation device.
 2. The charged particle beam irradiation apparatus according to claim 1, wherein said controller modifies the operating parameters of said charged particle beam generator such that a beam intensity level or beam size of the charged particle beam is changed according to the irradiation method adopted for said selected irradiation device.
 3. The charged particle beam irradiation apparatus according to claim 2, further including: a detector for detecting a beam state of the charged particle beam extracted from said charged particle beam generator; and a judging device for judging whether the beam state that has been detected is normal; wherein said controller modifies judgment parameters of said judging device according to the irradiation method adopted for said selected irradiation device.
 4. The charged particle beam irradiation apparatus according to claim 3, wherein: said detector detects a beam energy level and beam position of the charged particle beam; said judging device judges whether detection results by said detector stay within allowable ranges; and said controller modifies the allowable ranges used as judgment criteria by said judging device, according to the irradiation method adopted for said selected irradiation device.
 5. The charged particle beam irradiation apparatus according to claim 4, wherein said plurality of irradiation devices include an irradiation device that employs a scanning irradiation method.
 6. The charged particle beam irradiation apparatus according to claim 5, wherein said controller modifies operating parameters of said charged particle beam generator so that the beam intensity and beam size of the charged particle beam that exist when an irradiation device employing the scanning irradiation method is selected will be smaller than the beam intensity and beam size existing when an irradiation device employing an irradiation method other than the scanning irradiation method is selected.
 7. The charged particle beam irradiation apparatus according to claim 6, wherein said controller modifies judgment parameters of said judging device so that the allowable beam energy and beam position ranges used as judgment criteria by said judging device when an irradiation device employing the scanning irradiation method is selected will be narrower than the allowable ranges used as judgment criteria when an irradiation device employing an irradiation method other than the scanning irradiation method is selected.
 8. The charged particle beam irradiation apparatus according to claim 7, wherein said charged particle beam generator includes a synchrotron.
 9. The charged particle beam irradiation apparatus according to claim 8, wherein: said charged particle beam generator includes said synchrotron having a high-frequency beam extraction device for extracting the charged particle beam by applying high-frequency electric power to the beam; and said controller operates such that the voltage applied to said high-frequency beam extraction device when an irradiation device employing the scanning irradiation method is selected will be lower than the voltage applied when an irradiation device employing an irradiation method other than the scanning irradiation method is selected.
 10. The charged particle beam irradiation apparatus according to claim 8, wherein: said charged particle beam generator includes said synchrotron having a beam scraping device which, by inserting a beam scraper, cuts a part of the charged particle beam while the beam is circularly revolving within said synchrotron; and said controller operates such that a stroke through which the beam scraper is inserted by said beam scraping device when an irradiation device employing the scanning irradiation method is selected will be greater than a stroke through which the beam scraper is inserted when an irradiation device employing an irradiation method other than the scanning irradiation method is selected.
 11. The charged particle beam irradiation apparatus according to claim 3, further including a second controller which, if said judging device judged that the charged particle beam extracted from said charged particle beam generator is abnormal, stops further extraction of charged particle beams from said charged particle beam generator.
 12. A charged particle beam irradiation apparatus that irradiates an irradiation target with a charged particle beam, said apparatus comprising: a charged particle beam generator including a cyclotron which accelerates the charged particle beam; a plurality of irradiation devices each for irradiating the irradiation target with the charged particle beam, wherein at least a part of said irradiation device group applies a different irradiation method; a beam transport system for transporting the charged particle beam extracted from said charged particle beam generator, to selected one of said irradiation devices; and a controller that modifies operating parameters of said charged particle beam generator and of said beam transport system according to the irradiation method adopted for said selected irradiation device.
 13. The charged particle beam irradiation apparatus according to claim 12, further including: an energy adjusting system that changes energy of the charged particle beam extracted from said cyclotron; wherein said controller modifies operating parameters of said charged particle beam generator or of said energy adjusting system according to the irradiation method adopted for said selected irradiation device.
 14. The charged particle beam irradiation apparatus according to claim 13, wherein: said charged particle beam generator includes an ion source for emitting the charged particle beam to said cyclotron; and said controller modifies data settings of said ion source such that the beam intensity data settings of said ion source that exist when an irradiation device employing the scanning irradiation method is selected will be smaller than the beam intensity data settings existing when an irradiation device employing an irradiation method other than the scanning irradiation method is selected.
 15. The charged particle beam irradiation apparatus according to claim 13, including either; said energy adjusting system including an aperture device in which plural kinds of apertures each for cutting part of the charged particle beam extracted from said cyclotron are selectively equipped; or said beam transport system; wherein said controller selects each of the apertures such that the amount of beam cut when an irradiation device employing the scanning irradiation method is selected will be greater than the amount of beam cut when an irradiation device employing an irradiation method other than the scanning irradiation method is selected.
 16. A method of charged particle beam irradiation in which the charged particle beam generated by a charged particle beam generator is emitted in transported form to selected one of plural irradiation devices whose irradiation methods include a different irradiation method; wherein operating parameters of the charged particle beam generator are modified according to the irradiation method adopted for the selected irradiation device.
 17. The charged particle beam irradiation method according to claim 16, wherein the operating parameters of the charged particle beam generator are modified so that a beam intensity level and beam size of the charged particle beam are modified according to the irradiation method adopted for the selected irradiation device.
 18. The charged particle beam irradiation method according to claim 17, wherein judgment parameters for judging whether a beam state of the charged particle beam extracted from the charged particle beam generator is normal are modified according to the irradiation method adopted for the selected irradiation device.
 19. The charged particle beam irradiation method according to claim 18, wherein allowable ranges for judging whether a beam energy level and beam position of the charged particle beam are normal are modified according to the irradiation method adopted for the selected irradiation device.
 20. A method of charged particle beam irradiation in which the charged particle beam generated by a charged particle beam generator which includes a cyclotron is emitted in transported form to selected one of plural irradiation devices whose irradiation methods include a different irradiation method; wherein operating parameters of the charged particle beam generator and of the beam transport are modified according to the irradiation method adopted for the selected irradiation device.
 21. The charged particle beam irradiation apparatus according to claim 5, wherein said controller modifies operating parameters of said charged particle beam generator so that the beam intensity of the charged particle beam that exist when an irradiation device employing the scanning irradiation method is selected will be smaller than the beam intensity existing when an irradiation device employing an irradiation method other than the scanning irradiation method is selected. 